Hybrid mode repeater/re-driver for high speed digital video signaling

ABSTRACT

A system and a method are disclosed for a hybrid mode re-driver which, among other advantages, reduces power consumption while maintaining signal integrity. Equalization is performed on a signal to remove distortions such as inter-symbol interference. The signal is then analyzed and the quality of the signal is assessed. In some cases, retiming is then performed on the signal to remove additional signal distortions. In other cases, retiming is not performed and is transmitted to a driver while bypassing retiming components. When retiming components are bypassed, the retiming components are placed in a state of reduced power consumption to reduce system power consumption.

BACKGROUND

1. Field of Art

The disclosure generally relates to signal re-driver. More specifically,the disclosure relates to signal re-driver between a graphics processingunit and an external connector.

2. Description of the Related Art

Video can be transmitted from the graphics processing unit (GPU) of asystem to an external connector on the outside of a PCB which allowsvideo data to reach an external device. As the data rate of videostandards increase, signal integrity becomes an increasingly significantproblem to be addressed by system designers. One way to addressdiminished signal integrity is by re-driving or repeating the signalbetween the GPU and the external connector. Re-driving can removedistortion caused by system printed circuit board (PCB) traces and otherinternal connections.

Equalization and retiming based re-drivers can be used, but each hassignificant drawbacks. An equalization based re-driver can removeinter-symbol interference distortion caused by the channel from the GPUto the external connector, but is unable to remove other distortion suchas random jitter and duty cycle distortion. A retiming based re-drivercan clean up and re-shape video signals more thoroughly to address alldistortion at any operation speed, but consumes significantly morepower.

BRIEF DESCRIPTION OF DRAWINGS

The disclosed embodiments have other advantages and features which willbe more readily apparent from the detailed description, the appendedclaims, and the accompanying figures (or drawings). A brief introductionof the figures is below.

FIG. 1 is block diagram illustrating one example embodiment of are-driver between a GPU and external connector.

FIG. 1B illustrates one example of a high level block diagram of ahybrid mode re-driver between a GPU and external device.

FIG. 2 illustrates one example embodiment of a hybrid mode re-driverbetween a GPU and external device.

FIG. 3 illustrates one example embodiment of the retiming based portionof a hybrid re-driver.

FIG. 4 is a flow chart illustrating one example embodiment of a hybridmode re-driver.

DETAILED DESCRIPTION

The Figures (FIGS.) and the following description relate to preferredembodiments by way of illustration only. It should be noted that fromthe following discussion, alternative embodiments of the structures andmethods disclosed herein will be readily recognized as viablealternatives that may be employed without departing from the principlesof what is claimed.

Reference will now be made in detail to several embodiments, examples ofwhich are illustrated in the accompanying figures. It is noted thatwherever practicable similar or like reference numbers may be used inthe figures and may indicate similar or like functionality. The figuresdepict embodiments of the disclosed system (or method) for purposes ofillustration only. One skilled in the art will readily recognize fromthe following description that alternative embodiments of the structuresand methods illustrated herein may be employed without departing fromthe principles described herein.

Configuration Overview

Various embodiments provide a system and method for implementing asignal re-driver. The disclosed system and method can decrease the powerused in when re-driving a signal to mitigate signal distortions. In anexample embodiment, a hybrid mode re-driver enables transmission of asignal between a GPU and external connector with minimal signal loss.The hybrid re-driver performs equalization on signals to reduce certaindistortions such as inter-symbol interference. When sufficientlybeneficial, retiming is also performed on signals. If retiming is notperformed, the corresponding components can be put into a sleep mode oranother low power state. Although generally described for use inconjunction with video standards such as HDMI and DVI, the describedsystem and method can also be applied to any signal suffering fromdistortion.

Referring now to FIG. 1, illustrated is a block diagram of one exampleembodiment of a re-driver between a GPU and external connector to anexternal device. GPU 102 generates a video signal and outputs the signalto re-driver 104. In one embodiment, the video signal is in the HDMI(High-Definition Multimedia Interface) or DVI (Digital Visual Interface)video formats. The re-driver 104 is placed between the GPU 102 and anexternal connector 106 to reduce the signal distortion at the externalconnector 106. Without a re-driver, the signal outputted from the GPU102 may degrade significantly before reaching the external connector106. A signal is particularly susceptible to signal degradation when ahigh data rate is utilized. Re-driver 104 processes the signal to reducedistortion and transmits the signal to an external connector 106.Typically, the external connector 106 is coupled to an external device108.

FIG. 1B illustrates one example of a high level block diagram of ahybrid mode re-driver 104 between a GPU and an external device. There-driver includes an equalizing module 112, a mode selection module 114and a retiming module 116. A video signal is received at equalizingmodule 112. Equalizing module 112 then performs equalization on thesignal to remove jitter and various distortions from the signal. Afterequalization, the mode selection module 114 analyzes the signal todetermine if further operations should be performed on the signal by theretiming module 116. In one embodiment, the data rate of the signal andother various signal characteristics are included in the analysis. If itis determined that additional distortion is to be removed, retimingmodule 116 performs a second level of distortion removal on the signalbefore outputting the signal. On the other hand, if it is determinedthat no additional distortion is to be removed the mode selection module114 indicates that the signal should bypass the retiming module 116 andbe output. If the retiming module 116 is bypassed, components associatedwith the retiming module 116 can be turned off, put to sleep, orotherwise placed in a state of low power consumption to reduce overallpower consumption of the re-driver 104.

Turning next to FIG. 2, illustrated is one example embodiment of ahybrid mode re-driver between a GPU and external device. The re-driver104 includes an adaptive equalizer 204, a mode selector 206, a retimer208, a multiplexer (mux) 210 and a driver 212. In one embodiment, avideo signal is received from the GPU 102. Equalization is thenperformed on the received signal by the adaptive equalizer 204 to removejitter. Equalization also has the capability to reshape both theamplitude and timing of the signal. Equalization removes certaindistortion such as ISI (inter-symbol interference) which may be causedby the channel the signal is transmitted along. In one embodiment,equalization is a suitable filter for low data speed operations toreduce distortion.

The video signal is then transmitted to the mode selector 206. The modeselector 206 analyzes the video signal to determine whether additionaldistortion removal should be performed on the video signal. In oneembodiment, the data rate of the data signal is included in theanalysis. If additional distortion removal is to be performed such as inthe case of signals with a high data rate, the video signal is sent tothe retimer 208 which is able to better remove distortion from a signalthan equalization, but consumes significantly more power than theadaptive equalizer 204 alone. After being processed by the retimer 208,the video signal is transmitted to the mux 210. On the other hand, if itis determined that no further distortion removal is to be performed, thevideo signal is transmitted to the mux 210 while bypassing the retimer208. If the retimer is bypassed, the retimer, or a portion of thecomponents of the retimer, is turned off or placed in a state of lowpower consumption. In one embodiment, the instruction to enter a stateof low power consumption is sent from the mode selector 206. The modeselector also sets the mux 210 to receive the correct signal by settingthe mux 210 through select line 216. The mux 210 outputs the selectedvideo signal to the driver 212 which, in one embodiment, sends the videosignal to the external connector 116.

In one embodiment, the GPU 102 determines whether retiming should beperformed on the video signal that the GPU is outputting and controlsthe mode selector 206. The GPU 102 might select the level of distortionremoval that should be performed based on the resolution of thetransmitted video or the features of a scene that is being transmitted.The GPU 102 may also perform any analysis that may have been performedby mode selector.

Next, FIG. 3 illustrates one example embodiment of the retiming basedportion of a hybrid re-driver. In one embodiment, the retimer 208includes a clock and data recovery (CDR) module 302, an alignment module304 and a transmitter module 306. In one embodiment, a video signalreceived from the mode selector 206 is first processed by the CDR module302. The CDR module 302 performs clock and data recovery to accuratelyrecover all of the information from the originally transmitted videosignal. In one embodiment, the signal is de-serialized and the retimer208 has recovers the original video data contained in the signal.Alignment module 304 uses a generated clock to re-encode the signal andprepare it for transmission. Transmitter module 306 then serializes thedata and transmits the reconstructed video signal. By recovering thedata and reconstructing the video signal, all distortion is removed aslong as the original data is recoverable. The steps performed by themodules of the retimer 208 may be performed in any module as long asretimer 208 performs retiming based re-driving.

Turning to FIG. 4, illustrated is a flow chart of a process performedone example embodiment of a hybrid mode re-driver. Initially, a videosignal is received 401 from an external source such as a GPU.Equalization is performed 403 on the video signal to remove certainsignal distortions. The video signal is then analyzed to determinewhether it is suitable for retiming 405. In one embodiment, thisanalysis depends on data rate and signal quality. In some casesadditional distortion removal is justified and retiming is performed407. If the signal is of sufficient quality, retiming is bypassed 409and components associated with retiming are placed in a state of reducedpower consumption. This significantly reduces the power consumption ofthe system over time. Finally, the video signal is transmitted 411through a driver to an external connector or external device. Thedistortion removal mode used by the hybrid re-driver on a video signalcan be switched in real time based on the current conditions of thevideo signal.

The system and method described above enables mitigating the distortionof a signal while reducing power consumption. The mode selector assessesthe benefit of re-timing based re-driving of a signal. If sufficientlybeneficial, retiming is performed before transmitting the signal to anexternal connector. On the other hand, if no retiming is performed, thecomponents responsible for retiming are placed in a reduced powerconsumption state. Hence, signal integrity is maintained whileminimizing power draw when certain components are unused.

Throughout this specification, plural instances may implementcomponents, operations, or structures described as a single instance.Although individual operations of one or more methods are illustratedand described as separate operations, one or more of the individualoperations may be performed concurrently, and nothing requires that theoperations be performed in the order illustrated. Structures andfunctionality presented as separate components in example configurationsmay be implemented as a combined structure or component. Similarly,structures and functionality presented as a single component may beimplemented as separate components. These and other variations,modifications, additions, and improvements fall within the scope of thesubject matter herein.

Certain embodiments are described herein as including logic or a numberof components, modules, or mechanisms, e.g., as shown by example withFIGS. 3 and 4. Modules may constitute either software modules (e.g.,code embodied on a machine-readable medium or in a transmission signal)or hardware modules. A hardware module is tangible unit capable ofperforming certain operations and may be configured or arranged in acertain manner. In example embodiments, one or more computer systems(e.g., a standalone, client or server computer system) or one or morehardware modules of a computer system (e.g., a processor or a group ofprocessors) may be configured by software (e.g., an application orapplication portion) as a hardware module that operates to performcertain operations as described herein.

In various embodiments, a hardware module may be implementedmechanically or electronically. For example, a hardware module maycomprise dedicated circuitry or logic that is permanently configured(e.g., as a special-purpose processor, such as a field programmable gatearray (FPGA) or an application-specific integrated circuit (ASIC)) toperform certain operations. A hardware module may also compriseprogrammable logic or circuitry (e.g., within a general-purposeprocessor or other programmable processor) that is temporarilyconfigured by software to perform certain operations. It will beappreciated that the decision to implement a hardware modulemechanically, in dedicated and permanently configured circuitry, or intemporarily configured circuitry (e.g., configured by software) may bedriven by cost and time considerations.

The various operations of example methods described herein may beperformed, at least partially, by one or more processors that aretemporarily configured (e.g., by software) or permanently configured toperform the relevant operations. Whether temporarily or permanentlyconfigured, such processors may constitute processor-implemented modulesthat operate to perform one or more operations or functions. The modulesreferred to herein may, in some example embodiments, compriseprocessor-implemented modules.

Some portions of this specification are presented in terms of algorithmsor symbolic representations of operations (e.g., as in the example ofFIG. 4) on data stored as bits or binary digital signals within amachine memory (e.g., a computer memory). These algorithms or symbolicrepresentations are examples of techniques used by those of ordinaryskill in the data processing arts to convey the substance of their workto others skilled in the art. As used herein, an “algorithm” is aself-consistent sequence of operations or similar processing leading toa desired result. In this context, algorithms and operations involvephysical manipulation of physical quantities. Typically, but notnecessarily, such quantities may take the form of electrical, magnetic,or optical signals capable of being stored, accessed, transferred,combined, compared, or otherwise manipulated by a machine. It isconvenient at times, principally for reasons of common usage, to referto such signals using words such as “data,” “content,” “bits,” “values,”“elements,” “symbols,” “characters,” “terms,” “numbers,” “numerals,” orthe like. These words, however, are merely convenient labels and are tobe associated with appropriate physical quantities.

Unless specifically stated otherwise, discussions herein using wordssuch as “processing,” “computing,” “calculating,” “determining,”“presenting,” “displaying,” or the like may refer to actions orprocesses of a machine (e.g., a computer) that manipulates or transformsdata represented as physical (e.g., electronic, magnetic, or optical)quantities within one or more memories (e.g., volatile memory,non-volatile memory, or a combination thereof), registers, or othermachine components that receive, store, transmit, or displayinformation.

As used herein any reference to “one embodiment” or “an embodiment”means that a particular element, feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. The phrase “in one embodiment” in various places in thespecification is not necessarily all referring to the same embodiment.

Some embodiments may be described using the expression “coupled” and“connected” along with their derivatives. For example, some embodimentsmay be described using the term “coupled” to indicate that two or moreelements are in direct physical or electrical contact. The term“coupled,” however, may also mean that two or more elements are not indirect contact with each other, but yet still co-operate or interactwith each other. The embodiments are not limited in this context.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

In addition, use of the “a” or “an” are employed to describe elementsand components of the embodiments herein. This is done merely forconvenience and to give a general sense of the invention. Thisdescription should be read to include one or at least one and thesingular also includes the plural unless it is obvious that it is meantotherwise.

Upon reading this disclosure, those of skill in the art will appreciatestill additional alternative structural and functional designs for asystem and method for enabling maintaining signal integrity with reducedpower consumption through the disclosed principles herein. Thus, whileparticular embodiments and applications have been illustrated anddescribed, it is to be understood that the disclosed embodiments are notlimited to the precise construction and components disclosed herein.Various modifications, changes and variations, which will be apparent tothose skilled in the art, may be made in the arrangement, operation anddetails of the method and apparatus disclosed herein without departingfrom the spirit and scope defined in the appended claims.

What is claimed is:
 1. A method for signal re-driving, the methodcomprising: receiving, by a re-driving device, a video signal from agraphic processing unit; performing distortion removal on the receivedvideo signal using an equalizer to remove jitter from the receivedsignal; generating an equalized video signal by the equalizer analyzing,by a distortion mode selector, characteristics of the equalized videosignal, the characteristics of the equalized video signal including atleast data rate; determining, in real time by the distortion modeselector, whether to employ a retimer circuit to remove distortion fromthe equalized video signal or to bypass the retimer circuit based atleast in part on the analysis, the retimer circuit configured to receivethe equalized video signal from the adaptive equalizer circuit andgenerate a re-timed video signal by recovering a clock and datacomponents of the received video signal and transmitting a reconstructedvideo signal using the recovered clock; generating, by the distortionmode selector: a selection signal having a first state based on adetermination to re-time the equalized video signal using the retimercircuit, and the selection signal having a second state based on adetermination to bypass retiming the equalized video signal; responsiveto a determination to bypass retiming the equalized video signal,sending the selection signal having the second state to a multiplexerfor selecting the equalized video signal for output by the re-drivercircuit, and sending an instruction to the retimer circuit for reducingthe power consumption of the retimer circuit.
 2. The method of claim 1,wherein the video signal is in one of the HDMI (High-DefinitionMultimedia Interface) or DVI (Digital Visual Interface) formats.
 3. Amethod for signal re-driving, the method comprising: receiving a videosignal from a graphic processing unit; performing distortion removal onthe received video signal using an equalizer to remove jitter from thereceived signal; generating an equalized video signal by the equalizer;receiving a control signal indicating whether to bypass retiming theequalized video signal, the control signal generated based at least inpart on one or more features of the received video signal; responsive tothe control signal, bypass retiming the equalized video signal; reducingthe power consumption of a retimer circuit used to re-time the equalizedvideo signal; and outputting the equalized video signal.
 4. The methodof claim 3, wherein the control signal is received from the graphicprocessing unit.
 5. The method of claim 3, wherein the one or morefeatures of the video signal includes resolution of the received videosignal.
 6. The method of claim 3, wherein the one or more features ofthe video signal includes features of a scene in the received videosignal.
 7. A system for signal re-driving, the system comprising: anequalizer configured to: receive a video signal from a graphicprocessing unit; perform a first level of distortion removal to removejitter from the received signal; and generate an equalized video signalbased at least in part on performing the first level of distortionremoval on the received video signal; a distortion mode selector coupledto an output of the equalizer and configured to: receive a controlsignal indicating whether to bypass retiming the equalized video signal,the control signal generated based at least in part on one or morefeatures of the received video signal; and responsive to the controlsignal indicating to bypass retiming the equalized video signal,bypassing a retimer circuit configured to receive the equalized videosignal from the equalizer circuit and generate a re-timed video signalby recovering clock and data components of the received video signal andtransmitting a reconstructed video signal using the recovered clock; andreduce the power consumption of the retimer circuit.
 8. The system ofclaim 7, wherein the video signal is in one of the HDMI (High-DefinitionMultimedia Interface) or DVI (Digital Visual Interface) formats.
 9. Thesystem of claim 7, wherein the control signal is received from thegraphic processing unit.
 10. The system of claim 7, wherein the one ormore features of the video signal includes resolution of the receivedvideo signal.
 11. The system of claim 7, wherein the one or morefeatures of the video signal includes features of a scene in thereceived video signal.
 12. A computer program product for signalre-driving, the computer program product comprising a non-transitorycomputer-readable storage medium storing instructions that when executedcause at least one processor to perform the method comprising: receivinga video signal from a graphic processing unit; performing distortionremoval on the received video signal using an equalizer to remove jitterfrom the received signal; generating an equalized video signal by theequalizer; receiving a control signal indicating whether to bypassretiming the equalized video signal, the control signal generated basedat least in part on one or more features of the received video signal;responsive to the control signal, bypass retiming of the equalized videosignal; reducing the power consumption of a retimer circuit used tore-time the equalized video signal; and outputting the equalized videosignal after.
 13. The computer program product of claim 12, wherein theone or more features of the video signal are determined based at leastin part on analyzing the eye pattern of the video signal.
 14. Thecomputer program product of claim 12, wherein the video signal is in oneof the HDMI (High-Definition Multimedia Interface) or DVI (DigitalVisual Interface) formats. the video signal includes features of a scenein the received video signal.
 15. The computer program product of claim12, wherein the one or more features of the video signal includesresolution of the received video signal.
 16. The computer programproduct of claim 12, wherein the one or more features of the videosignal includes features of a scene in the received video signal.